This invention relates to a gas turbine combustion chamber with a burner, with means for the supply of fuel and with an atomizer.
Various forms of gas turbine combustion chambers are known from the state of the art.
For reduction of the pollutant load, in particular nitrogen oxide emissions, the fuel must generally be premixed with as much air as possible to obtain lean combustion, i.e. one characterized by air excess.
In the case of aircraft gas turbines, it is further necessary to obtain high overall efficiency and reduced nitrogen oxide emission. This calls for high energy turnover and correspondingly large fuel mass flows within the combustion chamber.
In the known combustion chambers, combustion is stabilized almost exclusively by means of swirling air promoting the re-circulation of the partly burned gases.
In the known designs, the fuel is introduced mostly centrally by means of a nozzle which is arranged on the center axis of an atomizer. Here, the fuel is often injected into the airflow with considerable overpressure so as to ensure adequate penetration and allow as much air as possible to be premixed with the fuel.
Such pressure atomizers are firstly designed to break up the fuel directly. In some designs of fuel injectors, the fuel is sprayed as completely as possible onto an atomizer lip. The fuel is accelerated by the airflow on the atomizer lip and atomized, or broken up, into fine droplets at the downstream end of the atomizer lip and mixed with the airflow.
In another form known from the state of the art, the fuel is applied to the atomizer lip by way of a so-called “film applicator”, with the fuel being distributed as uniformly as possible as a film.
Specification EP 0 935 095 A2 shows a gas turbine combustion chamber with an annular fuel supply line from which fuel is introduced into an airflow either at the outer circumference of the airflow or in a further inward zone.
In the state of the art, it is disadvantageous that the injection of fuel by means of a central nozzle or a pressure atomizer, respectively, as well as the discharge of fuel in the form of a film on a film applicator will not—or only to a limited extend—provide for homogenous mixing of the fuel with the passing combustion airflow. Advanced combustion chambers—which are optimized for reduced nitrogen oxide emissions—are characterized in that large amounts of air are to be mixed with fuel within narrow stoichiometric limits before being supplied to combustion. Consequently, a large amount of the air entering the combustion chamber must flow through the fuel nozzle and be premixed here with fuel before combustion in the combustion chamber takes place. This air quantity can amount to 70 percent of the entire combustion chamber air. Since, for said reasons, this amount of air is very large, appropriately dimensioned flow areas must be provided in the fuel conditioning system or the fuel nozzle, respectively. It is further disadvantageous that the fuel jets and sprays exiting through such nozzles will not provide for adequate penetration of the—constantly growing—air passages of the combustion chambers, as a result of which the homogenous distribution of the fuel/air mixture will be fully or partly impaired.